When plasma processing, e.g., plasma etching process, is performed on a wafer as a substrate by using a plasma generated from a CF-based processing gas, CF-based deposits generated by the CF-based processing gas may be attached to a wafer surface. The CF-based deposits attached to the wafer surface are removed by sputtering using the plasma (positive ion). However, a peripheral portion (hereinafter, referred to as a “beveled portion”) and a backside flat portion of the wafer is hardly sputtered by a plasma, so that the CF-based deposits attached thereto are not removed.
Thus, the CF-based deposits attached to the beveled portion and the backside flat portion are removed by a post-processing apparatus. To be specific, in the post-processing apparatus, a laser beam spot of, e.g., about Φ0.6 mm, is irradiated onto the beveled portion and the backside flat portion to heat them and, at the same time, ozone gas is supplied thereto. Due to chemical reaction therebetween, the CF-based deposits are decomposed into CO, CO2, and/or F2 and removed.
If a foreign substance removing process is carried out at a high speed in the post-processing apparatus for performing cleaning by removing foreign substances attached to the peripheral portion of the wafer by using a laser beam, materials other than organic materials may be peeled off from the surface of the wafer due to a sharp temperature increase. On the other hand, if the process is carried out at a low speed, processing time increases and, also, a heat transfer from the peripheral portion of the wafer to the surface of the wafer increases, thereby inflicting adverse effects on chips on the surface of the wafer. For that reason, there is required development of a technique capable of effectively removing foreign substances attached to a wafer by omitting unnecessary processes to minimize processing time and optimizing an amount of heat transfer into the wafer as a substrate to be processed.
Meanwhile, Patent Document 1 is a well-known document which discloses a prior art that optimizes processing by adjusting a position of a laser beam source with respect to a wafer as a substrate to be processed. In the Patent Document 1, a substrate processing apparatus includes a vacuum chuck for holding and rotating a wafer W in an approximately horizontal direction; and an optical etching device for irradiating laser beam onto a peripheral portion of the wafer W held by the vacuum chuck. This substrate processing apparatus removes a copper thin film from the peripheral portion of the wafer W by irradiating Xe laser beam onto the peripheral portion of the wafer W rotated while being held by the vacuum chuck, by the optical etching device which is positioned conforming to a size of an outer diameter of the wafer.    [Patent Document 1] Japanese Patent Laid-open Application No. 2003-197570
However, the prior art is disadvantageous in that the apparatus becomes complicated and scaled up because it requires a detection unit for detecting an outer diameter of the substrate to be processed in addition to a laser beam irradiation unit for processing a substrate. Besides, there is likelihood that the amount of heat transfer into the substrate to be processed is not optimized and a surface other than a target surface of the substrate to be processed is excessively heated.